1. Field of the Invention
This invention relates to a semiconductor element, particularly usable for a semiconductor light-emitting element such as a light-emitting diode.
2. Related Art Statement
Recently, much attention is paid to a GaN-based compound semiconductor (hereinafter, often called as a “GaN-based semiconductor”) as a semiconductor constituting a light-emitting layer of a blue light-emitting device. Such a GaN-based semiconductor is formed by a MOCVD method using a trimethylgallium as a Ga raw material gas and an ammonia gas as a N2 raw material gas on a substrate consisting of different materials such as sapphire.
However, if a light-emitting layer is made of such a GaN-based semiconductor, the crystal quality and the surface morphology of the light-emitting layer is deteriorated, so that a blue light can not be effectively generated and emitted from the layer.
In order to work out the problem, such an attempt is made in the Japanese Laid-open Publication Kokai Hei 4-297023 (JP A 4-297023) as forming a buffer layer made of a semiconductor nitride of GaaAl1-aN (0<a≦1), and thus, improving the crystallinity and the surface morphology of the light-emitting layer.
Particularly, however, the crystallinity can not be sufficiently improved by such a buffer layer, and thus, the luminous efficiency of a semiconductor light-emitting element can not be improved.